Rotary impact burrowing device



N V- 1969 G. A. REINOLD 3,480,092

ROTARY IMPACT BURROWING DEVICE Filed NOV- 8, 1 5 S Sheets-Sheet 1 INVENTOR G. A. R INOLO CQMIL {5. M,

A T TORNEY Nov. 25, 1969 e. A. REINOLD ROTARY IMPACT BURROWXNG DEVICE 5 Sheets-Sheet 2 Filed Nov. 8, 1967 N V- 1969 G. A. REINO'LD ROTARY IMPACT BURROWING DEVICE Filed Nov. 8, 1967 United States Fatent O 3,480,092 ROTARY IMPACT BURROWING DEVICE Gordon A. Reinold, Baltimore, Md., assignor to Bell Telephone Laboratories, Incorporated, Murray Hill, N.J., a corporation of New York Filed Nov. 8, 1967, Ser. No. 681,356 Int. Cl. E21b 11/02; B25d /02; E01g 3/00 US. Cl. 175-19 8 Claims ABSTRACT OF THE DISCLOSURE A self-propelled guidable underground missile is disclosed in which the propulsion unit is an auger driven by impact from a rotary missile member.

This invention relates to underground burrowing devices and more particularly to a self-propelled and guideable underground missile in which the propulsion system is based on an impact-driven auger.

BACKGROUND OF THE INVENTION The great bulk of existing communication and electrical cable and wire currently is located above-ground. With the continued growth of electrical usage and telephone communications, the concentration of this above-ground cable plant constitutes an ever-growing eyesore. The cost of placing such plant underground, in the first instance, however, has heretofore been prohibitively high.

One of the tools presently lacking in buried plant technology is a hole-digging device that can be guidably directed for short distances under existing real estate, such as roads, lawns, sidewalks, etc. Currently the only alternative to trenching across the face of a lawn or a road involves use of a compacting anger that works much like a wood screw pulling itself into the ground. Its disadvantage is that relatively rigid steel shafts are required to transmit torque to the auger; and hence it is not possible to vary the auger path away from a substantially straight line.

A new generation of devices now under development, called moles, promise to overcome the disadvantages of both the trenching method and the compacting auger mechanism. These devices involve a relatively stubby nosecone driven and guided by an attached power unit. In broad principle, the cone is advanced through the ground by repeated jolts delivered by the power unit.

The impact mechanism used in moles to date has been linear; and, hence, for a given actuating pressure the kinetie enery of the striking mass can only be increased at the expense of adding length to the mole. Length increases, however, reduce the capability of such a mole to be guided.

The mole of the present invention combines a rotary impacting device with a burrowing auger. Advantageously, there is no kinetic energy limitation similar to that characterizing the linear impact mole, since the angular excursion of the rotating impacting mass during acceleration can be arbitrarily large without a size penalty. Further, the impact principle of the present invention allows torque multiplication. That is, large soil resistances can be overcome with a low torque motor within the mole by storing momentum in a rotating mass and transferring it in sharp pulses to turn the auger. Of further advantage is the fact that the rotary impacting auger can be powered through a flexible lineeither electric or hydraulic. This, plus the moles relatively short length, greatly facilitate the guidance problem.

One broad object of the invention to be described, therefore, is to reduce the cost of burying aerial cable and Patented Nov. 25, 1969 An added object of the invention is to economically bury a wire or cable without resort to trenching through the surface.

A feature of the invention resides in the use of a rotary impacting device to drive an anger through the soil.

An added feature of the invention lies in the combination of a rotary impact driven auger with a guidance mechanism controlled from above ground.

The invention, its further objects, features, and advantages will be more fully apprehended from a reading of the description to follow of an illustrative embodiment thereof:

DESCRIPTION OF THE DRAWING FIG. 1 is a side perspective view in partial section of a mole employing the inventive principles;

FIG. 2 is a sectional perspective view principally of the rotary impact mechanism; and

FIGS. 3A-3D are sectional views further illustrating the impacting drive.

As seen in FIG. 1, the rotary impacting mole, designated generally as 10, comprises an auger head 11 with a tapered forward portion and auger flights 12 affixed on the outer surface thereof. Auger head 11 advantageously is fabricated of cast iron with the flights either machined or cast-in. The tapered forward portion of auger head 11 advantageously is a solid mass; while rearwardly thereof the head interior is hollow. Auger head 11 is rotatably mounted on the forward sleeve portion 13 of a housing 14 by means of two ball bearings 15, 16.

Fixedly mounted within the sleeve 13 is a non-rotating electric or hydraulic motor, designated 17. Motor 17 advantageously delivers a constant torque which results in a maximum eneregy transfer rate. Behind the forward sleeve 13, and rearwardly of motor 17, housing 14 advantageously is a solid mass. Guidance of mole 10 is accomplished through steering unit 20 disposed rearwardly of housing 14, in a manner to be described hereinafter.

The impact drive mechanisms are most clearly shown in FIG. 2. First, a rotatable hammer designated 21 is mounted through ball bearings 22, 23 in the hollow interior of head 11. Advantageously, the mass moment of inertia of hammer 21 with respect to that of auger head 11 is in the approximate ratio of 1:4. The rear of hammer 21 terminates in a flange, the interior periphery of which is provided with gear teeth 24. The remote interior of hammer 21 contains a cam 25 rigidly mounted on the shaft 26 of motor 17.

As seen in FIG. 2, motor 17 drives hammer 21 through gear 27 mounted on shaft 26, thence idler gear 28, and gears 29, 30 mounted on shaft 31, gear 30 engaging the interior gear 24 of hammer 21. Bearing plates 32, 33 are suitably affixed or fitted within the hollow interior rear portion of auger head 11 to provide bearing surfaces for the mentioned shafts.

Also mounted in hammer 21 are hammer jaws 34, 35 as shown in FIGS. 3A-3D. Jaws 34 and 35 are spaced apart in slotted sections of hammer 21; and are substantially elongated as shown in FIGS. 1 and 2. Anvils 38, 39 are cast axially along the interior surface of anger head 11 and are substantially coextensive in length with hammers 34, 35. Bow spring pairs 36, 37 maintain jaws 34, 35 respectively in their withdrawn position as shown in FIG. 3C. In this position, jaws 34, 35 rest on the low portion of cam 25. In their raised position, as depicted in FIG. 3A, as well as in FIGS. 1 and 2, jaws 34, 35 are in striking relation with anvils 38, 39.

OPERATION Once mole 10 is introduced into the ground, propulsion occurs in the following fashion: motor 17 accelerates hammer 21 through an angle that can be arbitrarily large, thus to build up a desirably high kinetic energy of rotation in hammer 21. Hammer 21 is accelerated with the jaws 34, 35 withdrawn and then raised into striking relation with anvils 38, 39 by action of the cam 25. The ratios of gears 27, 29, 30 and 24 are chosen so that cam 25 will raise jaws 34, 35 every nth rotation of hammer 21. At or just before the time of impact between jaws and anvil the lobe of cam 25 will move out from under the jaws 34, 35 as shown in FIG. 3B. A typical value of n is one. The sequence of operation is illustrated in the following paragraph.

As seen in FIG. 3A, the position of the cam lobes of cam 25, the jaws 34, 35 and the anvils 38, 39 are such that jaws 34, 35 are raised into engaging relation with the anvils just prior to impact. The opposed jaws 34, 35 are forced to their outermost limits of travel against the force of spring pairs 36, 37. At this point hammer 21 has accelerated to its highest level of kinetic energy. FIG. 3B shows the cam lobes of cam 25 moving out from under the jaws 34, 35 just prior to impact and before the springs 36, 37 have taken effect to begin returning the jaws to their withdrawn position. After impact, hammer 21 and motor 17 to which it is connected, tend to rebound but the rebound is minimal because of the constant clockwise force of motor 17. FIG. 30 illustrates the component positions at the point of zero acceleration of hammer 21 at which time springs 36, 37 return the jaws 34, 35 to their withdrawn position in contact with cam 22. FIG. 3D indicates the position of the components as they commence a predetermined number of revolutions of hammer 21 for the kinetic energy buildup.

Depending upon the mass moment of inertia of the hammer, the auger, the desired energy transfer rate, and the attainable motor torque, it is possible to preselect the number of degrees of rotation of hammer 21 before the cam lobes catch up with their slightly faster angular velocity to raise the jaws. Thus, after an advantageously chosen number of degrees of rotation of hammer 21, an impact blow is delivered through the jaws 34, 35 to the anvils 38, 39. A large impact torque is transmitted to auger head 11 causing it to advance into the soil. A number of such impacts can be delivered per second, depending upon the amount of motor torque, and the desired amount of energy per impact.

For example, a hammer weight of 18 pounds and hammer diameter of 2 inches results in a rotary inertia of pounds-inch-seconds squared. Such a rotor to store 2,000 inch-pounds of kinetic energy must be spun at a speed of 414 radians per second. A rotor having the above characteristics driven by a motor of characteristic M=20 (l(w/5000) would require approximately 54 milliseconds to be accelerated to that speed. It follows that up to 20 impact blows can be delivered per second, Which would give a turning rate to an auger whose mass moment of inertia is approximately 4 of approximately 1.35 radians per second, and a total linear advance of the mole in the neighborhood of approximately inches per minute.

Section 20 in the rear of mole 10 comprises one method for steering the mole. The axial attitude of section 20 may be adjusted through a spherical angle of about 30. Section 20 consists of a rubber portion 41 abutting the rear end of solid housing 14. Within section 41 are mounted a number of cylinders for example, eight, with pistons 42. Aft of rubber section 41 is a control section 43 in which is located equipment for actuating selective ones of the pistons 42 through suitable control means at ground level. It thereby is possible to flex the tail section 20 in fishtail fashion and thus force the mole to follow a curved rather than a straight path. Other means for steering the mole in X-Y-Z space may be readily envisioned by persons skilled in the art.

It is to be understood that the embodiments described herein are merely illustrative of the principles of the invention. Various modifications may be made thereto by persons skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. A burrowing device comprising a rotatable auger head including internal anvil means, an inertial member including extensible hammer jaws, means for angularly accelerating said inertial member, and means responsive to attainment of a prescribed level of kinetic energy by said inertial member for extending said jaws into impacting contact with said anvil means.

2. A burrowing device in accordance with claim 1 wherein said accelerating means comprises a constant torque motor.

3. A burrowing device in accordance with claim 2, further comprising a tail extension swivelably attached to the after end of said device, and means for controlling the attitude of said extension with respect to said device proper, thereby to controllably guide said device through soil.

4. A burrowing device in accordance with claim 2 wherein said anvil means comprises a pair of opposed elongated ridges longitudinally disposed within said auger head; and said hammer jaws comprise a pair of elongated massive metallic ribs coextensive in length with said ridges and disposed parallel thereto.

5. An underground burrowing device comprising:

a tapered cylindrical forward section including auger flutes disposed along the exterior thereof and anvil means in the interior;

a cylindrical housing including means for rotatably mounting said forward section thereon;

a rotatable hammer disposed within said forward section and including radially movable jaw means;

motor means fixedly mounted in said housing and connected to said hammer for accelerating same; and

means for periodically extending said jaw means into impacting engagement with said anvil means, the impact blow driving said flutes forward in the ground and thus advancing said burrowing device in the soil.

6. An underground burrowing device comprising a fluted cone with a hollow interior and means for delivering to said cone interior repeated impact blows tending to rotate said cone in the direction of advance of said flutes.

7. The device claimed in claim 6, further comprising means for guiding the course of advance of said device in X-Y-Z space.

8. The device claimed in claim 6, further comprising means for attaching an electrical cable or the like to the after end of said device, said cable being pulled along behind the device as it advances.

References Cited UNITED STATES PATENTS 2,540,161 2/1951 Boclen 173-93 2,650,314 8/1953 Hennigh et al 17597 X 2,864,633 12/1958 Mackie 52l57 X 2,999,572 9/1961 Hinckley 17598 X 3,326,008 6/1967 Baran et a1 175-19 X 3,330,368 7/1967 Baran et al 175-94 3,375,885 4/1968 Scott et al 17594 X CHARLES E. OCONNELL, Primary Examiner R. E. FAVREAU, Assistant Examiner US. Cl. X.R. 

